Re: Difference between Design and Architecture

Robert Martin wrote:

When you break the software up like this, you also break the software. You introduce bugs that can be very hard to find. However, if you have written the application using TDD; you have tests that can show you when you have broken functionality. Thus the tests allow you to make the changes with full knowledge of the side effects.

I am slightly confused here. Do you use "TDD" and "tests" as synonyms,
or are you implying that TDD is the only way to produce tests?

The tests are the lubricant that make the changes much more reliable. The tests also allow the changes to be made incrementally. Thus TDD is a major aid to scalability.

Aren't you comparing apples and oranges? It seems to me that you are
arguing, analogically speaking, that a seat-belt is more important than
a map when you have to drive to a new place. However, both serve
different purposes.

You have argued, to use software architecture terms, that testability is
important because it affects reliability, which is just fine. However,
reliability is not scalability.

You have argued that tests are important to restructuring, which is also
fine. However, restructuring is directionless, whereas architecture is
about direction.

Architecture will help you to make scalability decisions about:

o Centralized versus distributed architecture
o Concurrency
o Load-balancing
o Data strategies (e.g. stateful versus stateless servers)
o I/O strategies (e.g. synchronous versus asynchronous interaction)
o Caching strategies

If you wish to argue that TDD is more important than architecture, then
you need to start by addressing how TDD helps me to make these
decisions.

--
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